I am using PIC18F4520. The project requirement is to interface GSM module with uC as well as receive commands from PC via serial port.
to achieve this I have connected Microcontroller- TX to GSM module- RX, as GSM module is used just for sending SMS. It is working OK with this connection.(this connection is on TTL level.)
but i want to receive command from PC , so I have connected PC- TX to uC -RX (this connection is through MAX232). when i connect PC-TX to uC-RX the serial terminal s/w (PC) shows garbage values on RX, and uC also receives garbage values (As I am not sending anything but still Receive interrupt routines gets called continuously ) . there is no issue in program.
but meanwhile the GSM module working fine.
Do i need to terminate the TX line? I am using just 2 wire serial cable for connection to PC.